PS/laponite nanocomposites were prepared by a solution blending method. Laponite used was organically modified by octadecyltrimethylammonium bromide (OCTA), octyltrimethylammonium bromide (OCTYL) and di(hydrogenated tallow) dimethylammonium chloride (2HT) at various surfactant loadings. Exfoliated nanocomposite structure was probably obtained when 2HT was used as laponite modifier, yet conventional composites were received in cases using OCTA and OCTYL, as shown by X-ray diffraction measurements. Thermal stability and mechanical properties were evaluated and correlated to the obtained composite's structure. Enhancement in water barrier properties was observed for exfoliated PS-nanocomposites compared to that of pristine polymer.
INTRODUCTIONInterest in polymer-layered silicate (PLS) nanocomposites has increased rapidly during the last 15 years. at an unprecedented level, both in industry and in academia, due to their potential for enhanced physical, chemical, and mechanical properties, compared to conventional composites [1][2][3][4][5][6] . They have the potential of being a low-cost alternative to high-performance composites for commercial applications in both the automotive and packaging industries. Polymer nanocomposites are two-phase materials in which the polymers are reinforced by nanoscale fillers. Depending on the nature of the components used (layered silicate, organic cation and polymer matrix) and the method of preparation, three main types of composites may be obtained when layered silicates are associated with a polymer: (a) phase separated microcomposite; (b) intercalated nanocomposite; and, (c) exfoliated nanocomposite [7] .Much effort has also been devoted to polystyrene clay nanocomposites [8][9][10][11][12] , using mainly montmorillonite as filler. Polystyrene=laponite nanocomposites have been reported rarely [13][14][15][16] . Mitchell et al. [13] studied the rheological